Question:
What are oxides?
10 Oxide Experiments
Here are 10 ways to experiment with oxides.
1. Brush oxides on greenware, bisque and/or glaze.
2. Make some slip and add some oxides to create colors. To get more uniform colors mix well.
To get more random, blotchy colors don't mix too well.
3. Brush oxide wash over an unfired glaze, then fire. Be very careful when handling as you may smudge the oxide.
4.. Brush oxides on, then apply glaze. Best to dip or spray to avoid brushing the oxide off (and if dipping, best to put some glaze aside so oxide doesn't contaminate your whole batch of glaze.)
Generally the stronger the oxide wash, the more it will bleed through the glaze.
* Both 2 and 3 works well with Opulence glazes, and many of the other glazes. Where specified by the manufacturer this is explained on the label.
5. Mix ball clay with your oxide/water. Is reported to gives a better consistency and tones down the color.
6. Brush a couple different oxides on, overlapping in areas.
7. Sgraffito. Brush on oxide. When dry, scratch with a sharp tool through the oxide to show the clay underneath. Cover with transparent or translucent glaze. Or do the same thing with oxide over unfired glaze.
8. Spatter wax on the surface, and paint the oxide wash over that.
9. Use other masking techniques, such as torn, wet newspaper, and paint an oxide wash over it.
10. Sprinkle a variety of different oxides on a newspaper. Place leather hard objects onto the oxide mixture (for example, a piece of tile). Or use a piece of Styrofoam or a sponge to pick up the oxide and transfer it to your piece. Keep the pattern as it lands, or smear it around. In this bisque and apply glazes; the oxides will still interact with the glazes when fired together.
Oxides compared to stains
How does oxide compare to stain? An oxide is a raw material. A stain is a commercial blend of raw materials (including oxides) to achieve an accurate, consistent color. Glazes and slips made with stain will generally be more uniform, whereas those made with oxide will be more splotchy, speckly, and variable (in other words, beautiful!). There are 4 main colorants used. Sometimes you will see them as oxides, sometimes as carbonates. For example, cobalt oxide and cobalt carbonate. The oxides are generally stronger in color and coarser grained (more speckly.) The carbonates are generally finer grained.
Adding Oxides
Oxides can be added to clay (mix with water then knead in), but this is expensive for deep coloring of large pieces. They can be added to slip or glazes. At stoneware temperatures, they can also or used on their own. Mix with water (mix often as it settles fast), brush on bisque, fire.
This is a way to get colored but still “natural” looking surfaces.
Copper
Copper Carbonate and Copper Oxide. (Note: Copper should not be used in soluble glazes for food and drink containers; in addition to not being safe, it will leach into tea for example, making your tea have a coppery taste.) Not very effective used on it's own. Better to add to or cover with glaze. In an electric kiln it will create a variety of green shades.
In alkaline glazes it will create turquoises. It may achieve red colors in a reduction kiln.
Cobalt
Cobalt Carbonate and Cobalt Oxide. This is the most powerful color and produces various shades of blue. It can be harsh used by itself, so is sometimes mixed with iron, manganese, magnesium or copper to create more subtle colors. Like iron oxide, it can be added to glaze, or can be applied to the clay surface and fired to stoneware temperatures. By itself it will tend to create a dark slate metallic finish.
It can be mixed with manganese and iron to produce rich black slips.
Manganese
Manganese Dioxide and Manganese Carbonate. In glazes creates colors such as mauve, purple and brown depending on the other ingredients present. By itself it produces an attractive brown with tiny metallic specks at stoneware temperatures (dioxide is specklier than carbonate).
It is often mixed with other oxides such as cobalt to create purples and iron to produce rich browns.
Iron Oxide
Iron Oxide. This comes in many varieties and can provide a wide variety of colors under different firing conditions. Types of iron oxide are red iron oxide, black iron oxide, and yellow ochre. At earthenware temperatures, up to 4 percent oxide will produce amber and honey glazes.
At stoneware temperatures it can be applied directly to stain the clay surface. It is often used in this way to highlight textured surfaces. Can also be added to glazes.
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| Jolyn Wells-Moran |
